We scoured the hundreds of Chrome extensions designed for Gmail. These are the best.

We scoured the hundreds of Chrome extensions designed for Gmail — whether they modify the UI of the webmail service, or add new features to it — and picked the best. Emphasis was placed on extensions that are free, and not tied to another site, web app, or other online service.

This extension adds up to four buttons to the right of the ‘checkbox’, ‘starring’, and ‘mark-as-important’ functions that are to the left of every message listed in your Gmail account main page. These extra buttons let you archive, delete, mark as spam, or mark as read/unread an email by simply clicking the button, without needing to open the message, or needing to click its checkbox first and then selecting whichever of these four operations you want.

A paperclip icon to the right of a message listed in your Gmail main window represents that a file or files are attached to that email. This extension determines what kind of file is actually attached, and changes the paperclip icon to a more specific image. So, if it’s a PDF, the attachment icon becomes a tiny image of a PDF document symbol. Attachment Icons for Gmail can recognize and assign unique icons for several file formats, which include media (images, sound, video) and Microsoft Office (Excel, PowerPoint, Word).

This extension is the very popular, with over 800,000 users recorded by Google. Checker Plus for Gmail notifies you of new emails with pop-up windows, which show a preview of an email’s first few lines, in the lower-right corner of your OS’ desktop. By clicking its icon in the Chrome extensions toolbar, not only can you glance through first-line previews of your new emails, you can do most email management functions without ever needing to open the Gmail main page. You can even compose a new email directly from the extension — again, without having to go to the Gmail main page. The settings to adjust the UI of Checker Plus for Gmail are many, and intimidating to go through. Fortunately, its default settings will probably satisfy most of your needs.

This is one of the most impressive Chrome extensions for Gmail that has been recently released: Copy cells from an Excel spreadsheet, and you can paste them into an email you’re writing by clicking a button that this extension adds to the email composer toolbar. The data and formatting of the cells, including their colors and sizes, will remain intact. (The email must be written with “plain text mode” off.) Your recipient will also see them in their original format. We found this extension also worked with other spreadsheet programs, like Google Sheets.

In the Gmail main page, the email label categories and Google Hangouts chat windows share the left column, and you can adjust the sizing they share with one another by dragging down or up the horizontal border between them. This extension adds a resizable vertical line between this column and the panel listing your messages. So by dragging this boundary side-to-side, you can adjust to your liking the width of the first column in relation to the panel.

Gmelius provides settings to modify big and small details of the Gmail UI, such as: removing from the main page the Hangouts window or header, which contains the Google logo and search box). (The search button will then work as a switch that you click to hide and unhide the header.) It can also strip out the “People” widget that shows up whenever you view an opened email. Gmelius can add various things, some of which are handled by other extensions in this article: highlighting the listing of an email in the main page with a color when you move the pointer over it, and changing the paperclip icon to represent what exactly an attached file is.

If you don’t need all the features of Checker Plus for Gmail, or prefer a Gmail checking extension that uses fewer system resources, then multiNotifier gets the job done. It can check up to five Gmail accounts, giving you a preview of the first line of each unread email when you click its extension button. Notification windows pop up from the lower-right corner of your OS’ desktop environment, each showing the first snippet of text from a newly arrived email.

If you’d like a free tool to block email trackers, try PixelBlock. It automatically prevents a tracking service from being notified when you’ve opened an email sent to you through it. PixelBlock marks tracked emails with a crossed-out red-eye icon by the sender’s name listed in an opened email. Clicking this icon reveals the name of the tracking service, if it can be identified.

Normally, when you turn on Google Tasks in Gmail, this to do tool appears as a pop-up window at the lower-right corner of the main page. RightTasks for Gmail sets Google Tasks inside a new column to the right of the panel listing your emails. This column can be neatly stowed away by clicking a button on its title bar, which turns it into a skinny vertical black bar. Clicking this bar brings back the column containing Google Tasks.

From the developer of Attachments Icons for Gmail, this extension, like the Gmelius suite, highlights the listing of an email in the main page with a color when you hover the pointer over it. The highlight color can be customized to be whatever you want, and you can select two colors to differentiate between an email that’s marked as read or unread.

After you install this extension: In Gmail’s main page, click the checkbox by the listing of an email, but continue holding down the mouse (or touchpad) button and then move down or up: The listings of other emails below or above will be highlighted and their respective checkboxes will become checked when the highlight sweeps over them, and unchecked as you move the highlighting away from them.

For some reason, Google didn’t include the ability to format any of the text you write in an email with strikethroughs. This extension simply adds this; it seamlessly integrates a strikethrough button among the other styles in the text formatting toolbar of the email composer window.

UglyEmail doesn’t block tracked emails from reporting back to their senders when you open them. Instead, in the main page, it marks received emails that are being tracked with a black eye icon by their listings. So you can see which are being tracked before opening them. The caveat in the present version of UglyEmail is that it doesn’t appear to mark emails that are being tracked from an anonymous source.